In general, the present invention relates to agricultural compositions containing glyphosate salts. More specifically, the present invention is directed to agricultural compositions formulated as liquid concentrates containing a glyphosate isopropylammonium salt.
Typically, commercially available agricultural compositions of glyphosate salts are formulated as liquid concentrates that can be readily shipped to consumers. It is desirable to provide a high-strength formulation to reduce shipping and handling costs and to reduce the amount of packaging material that must be disposed. There is often a trade off between providing a highly concentrated herbicide composition to reduce shipping and handling costs and ensuring that the consumer can conveniently use and dilute the concentrate. Increasing the concentration of the active ingredients in the composition can increase the composition""s viscosity.
The herbicidal formulations typically include an efficacy-enhancing surfactant. Inclusion of a surfactant is highly desirable because the resulting formulation exhibits a substantially increased herbicidal activity. However, selected surfactants either can interact with the glyphosate salt, increasing the viscosity of the herbicidal formulation, or are generally incompatible with the glyphosate salt solution. Certain surfactants, for example, some of the surfactants in the polyoxyalkylene alkylamine class of compounds, when combined with the glyphosate salt, increase the viscosity of the formulation.
A highly viscous concentrate is difficult for the consumer to use. If the viscosity is too high, handling of the concentrated herbicide can be difficult. Furthermore, highly viscous liquids are difficult to accurately measure, either for application to the plants or for dilution to a less concentrated spray solution. These problems can be further acerbated for agricultural formulations used in the late winter and early spring when the temperatures are generally low. The viscosity of the concentrated agricultural formulations becomes even greater at low temperatures. This makes it even more difficult to dispense or pump and to accurately measure the concentrate.
Additionally, the high-strength formulations should be stable and retain potency during storage and shipping. One or more of the components in a highly concentrated formulation can precipitate or separate from the bulk solution. Consequently, the consumer must redissolve or re-suspend all of the components before use or dilution. It is desirable that the herbicide concentrate be stable at temperatures at least as high as 50xc2x0 C. and should not exhibit any precipitation or sedimentation at temperatures as low as 0xc2x0 C.
Surprisingly it has been found that the viscosity of a concentrated aqueous glyphosate isopropylammonium salt formulation depends upon the molar ratio of glyphosate acid equivalent to isopropylamine. Typically glyphosate isopropylammonium salt concentrates are prepared with about 15%-20% excess isopropylamine, i.e., from a 1.00:1.15 to a 1:00:1.20 molar ratio of glyphosate acid equivalent to isopropylamine. The excess isopropylamine is used to increase the solubility of glyphosate isopropylamine salt at very low temperatures. Generally the glyphosate isopropylammonium salt is prepared as a liquid manufacturing-use concentrate containing 62% glyphosate isopropylammonium salt, which is subsequently formulated into the final product by diluting with water and adding the desired additives, e.g,. an activity enhancing surfactant. A drawback of using the 62% glyphosate isopropylammonium salt manufacturing-use concentrate with an excess of isopropylamine to prepare highly concentrated formulations containing glyphosate isopropylammonium salt in combination with an activity enhancing surfactant is the high viscosity of the resulting product. It has now been found that the viscosity of concentrated glyphosate isopropylammonium formulations can be lowered significantly by using a glyphosate acid equivalent to isopropylamine molar ratio of about 1.00:1.10, and more preferably between about 1:00:1.05, whilst still providing satisfactory stability of the formulation at low temperatures.
The present invention provides a herbicide concentrate comprising: glyphosate isopropylammonium salt, which is dissolved in an aqueous solution at a concentration of greater than about 400 gram acid equivalents per liter (gae/l) based upon glyphosate acid. The glyphosate isopropylammonium salt is prepared by combining glyphosate acid and isopropyl amine at a molar ratio of between about 1.00:1.00 and about 1.00:1.10 (glyphosate acid:isopropyl amine), preferably between 1.00:1.00 and about 1.00:1.05. The concentrate also includes a polyoxyalkylene alkylamine surfactant.
In another form, the present invention provides a herbicide concentrate that comprises an aqueous solution that includes a herbicide component comprising greater than about 400 gae/l of a glyphosate isopropylammonium salt; and a surfactant component including a polyoxyalkylene alkylamine. In this form of the invention the aqueous solution contains less than about 10 molar % excess isopropyl amine, based upon the glyphosate isopropylammonium salt, more preferably the aqueous solution contains less than about 5 molar % excess isopropyl amine, still more preferably the aqueous solution is essentially free of any excess isopropyl amine.
In still yet another form, the present invention provides a method of reducing the viscosity of a concentrated herbicide composition containing a glyphosate salt and a polyoxyalkylene alkylamine surfactant. The method comprises combining glyphosate acid with between about 1 and about 1.10 equivalents of isopropyl amine, based upon the molar equivalents of the glyphosate acid, to provide a glyphosate isopropylammonium salt. The glyphosate isopropylammonium salt is combined with a polyoxyalkylene alkylamine surfactant.
The agricultural formulation provided in the present invention can be formulated and distributed as a highly concentrated solution that exhibits a low viscosity. This formulation can be subsequently diluted to a desired concentration by an end user for use on and around plants.
The present invention provides highly concentrated agricultural formulations that contain a glyphosate salt and a surfactant. The glyphosate salt is a glyphosate isopropylammonium salt that is specifically formulated to provide a concentrated solution that exhibits low viscosity. The agricultural composition also includes at least one surfactant, preferably a polyoxyalkylene alkylamine surfactant.
It has been determined that a concentrated solution can be prepared by selectively combining about one molar equivalent isopropylamine with about one molar equivalent glyphosate acid in a desired amount of water. The resulting concentrate glyphosate salt composition can be combined with an effective amount of an efficacy-enhancing surfactant. The resulting concentrated solution unexpectedly exhibits a viscosity that is lower than the viscosity of similar compositions, which contain an excess of isopropylamine.
The concentrate of the present invention contains a high concentration of glyphosate as an isopropylammonium salt dissolved in water. In preferred embodiments, the concentration of the glyphosate isopropylammonium salt is selected to be greater than about 400 gram acid equivalents of the glyphosate acid per liter of solution (gae/l), more preferably greater than about 450 gae/l. The upper limit of the glyphosate salt concentration is less than that which would separate out or precipitate from solution at ambient temperature.
The glyphosate salt formulation can be prepared by suspending glyphosate acid in a minimal amount of water and slowly adding one equivalent of isopropylamine to prepare the desired salt solution. Then the surfactant can be added to the clear, homogeneous salt solution. Preferably, the formulation is prepared and maintained below about 50xc2x0 C. The concentrated formulations of the present invention can also be prepared substantially as described in EP 290,416 and U.S. Pat. No. 4,612,034xe2x80x94albeit using about a 1:1 molar ratio of glyphosate:isopropylamine instead of using an excess of the amine as prescribed by these references. The resulting formulations were found to be storage stable at a high concentration and higher strengthxe2x80x94yet having a low viscosity.
The herbicide concentrate of the present invention can include a slight excess of isopropyl amine. An excess of isopropyl amine is that amount of isopropyl amine greater than the amount of glyphosate initially added to the solution or greater than one equivalent of the glyphosate acid used to prepare the herbicide concentrate. In preferred embodiments, the herbicide concentrate of the present invention includes between about 1.00 equivalents and about 1.10 equivalents isopropyl amine/isopropylammonium cation based on the moles of glyphosate used to initially prepare the herbicide concentrate. More preferably the present invention includes between about 1.00 equivalents and about 1.05 equivalents isopropyl amine/isopropylammonium cation.
The herbicidal concentrate also includes a polyoxyalkylene alkylamine surfactant. Nonlimiting examples of surfactants useful in the present invention include: polyoxyalkylene derivatives of soyamine, tallowamine, and cocoamine. In preferred embodiments of the present invention the surfactant is selected to be a polyoxyalkylene tallow amine or polyoxyalkylene cocoa amine having between 2 and 15 ethylene oxide groups (EO) per amine. More preferred surfactants include a polyoxyalkylene tallow amine or polyoxyalkylene cocoa amine having between 5 and 10 EO per amine.
The herbicidal concentrate also includes a polyoxyalkylene alkylamine surfactant in a herbicidally efficacious amount. More preferably the concentrate includes the surfactant in an amount greater than about 60 grams per liter (g/l), more preferably greater than about 100 g/l. The upper concentration limit of the surfactant is governed by the amount of glyphosate isopropylammonium salt present in the formulation.
The agricultural compositions prepared according to the present invention are highly effective as a herbicide composition against a variety of weeds. The formulations of the present invention can be used as is or combined with other components including other agriculturally acceptable adjuvants commonly used in formulated agricultural products, such as antifoam agents, compatibilizing agents, sequestering agents, neutralizing agents and buffers, corrosion inhibitors, dyes, odorants, penetration aids, wetting agents, spreading agents, dispersing agents, thickening agents, freeze point depressants, antimicrobial agents, crop oil, other biologically and/or agriculturally active components and the like. The concentrated agricultural formulations are typically diluted in water and then applied by conventional means well known to those in the art.
It has been unexpectedly determined that the viscosity of a concentrated glyphosate isopropylammonium salt solution can be varied by altering the amount of isopropyl amine included in the solution. As noted above, commercial herbicide formulations are prepared by reacting glyphosate acid with an excess amount of a base such as isopropyl amine. The present invention provides a highly concentrated glyphosate isopropylammonium salt solution that exhibits significantly reduced viscosity compared with known commercial products having comparable concentrations. In preferred embodiments, the herbicide concentrates of the present invention exhibit a viscosity of less than about 200 cP measured on a Brookfield LVT viscometer with a #2 spindle at 20xc2x0 C. More preferably the present invention provides a herbicide concentrate having a viscosity of less than about 180 cP, still more preferably less than about 160 cP, measured as above noted.